1. Field of the Invention
One or more embodiments of the present invention relate to a protective element that protects a circuit connected onto a current path by causing a blowout to the current path, a method for manufacturing such a protective element, and a battery module in which the protective element is embedded.
2. Background Art
In general, a charging and discharging circuit for a secondary battery, such as a lithium ion battery or the like, has a function for shutting down an output of the battery by activating many protective circuits (Patent Document 1).
In the case when this charging and discharging circuit is normally operated, the output is turned ON/OFF by using an FET transistor; however, because an instantaneous heavy current, such as typically represented by a lightening surge, tends to exceed the operation time of the FET transistor, a protective circuit such as a fuse for detecting an overcurrent to cause a shutdown is used as a protective circuit from the viewpoint of protecting inner circuits. Moreover, an FET is used so as to monitor the state of a battery and shut down the output of the battery, when an abnormal state, such as an overcharge, an overdischarge, heat generation or the like of the battery, is detected.
Moreover, as described in Patent Document 2, the safety of a secondary battery is ensured by using multiple protective circuits having a protective element that compulsorily shuts down a charging operation to a buttery, in the case when, upon charging a secondary battery, a detection of an overcharge to the battery, an abnormal temperature rise of the battery, an erroneous operation due to heat generation of the FET occurs.
Moreover, as described in Patent Document 3, as a protective element for a protective circuit for such a lithium ion secondary battery, a structure has been generally known in which a heating body is formed in the protective element, and by using this heating body, a low-melting point metal on a current path is blown out.